1. Technical Field
The present invention relates to a video signal transmission apparatus, an identification information acquisition method for a video signal transmission system, and a computer readable medium storing an identification information acquisition program for a video signal transmission system.
2. Related Art
A serial data signal for a digital video so called a DVI (Digital Visual Interface) or HDMI (High Definition Multimedia Interface) requires high-speed signal which is equal to or higher than 1 Gbps. Therefore, such signal can be transmitted only up to about 10 m, when transmitted by an electric cable. Accordingly, when transmission of such signal for more than 10 m is required, the serial data signal needs to be converted into an optical signal and an optical fiber may be used to transfer such optical signal. In the case of using the optical fiber, an optical transmitter and an optical receiver, connected to both ends of the optical fiber, may be provided between a video source device such as a PC (including a video card) and a sink device such as a display.
The serial data signal includes a high-speed video signal, information of the display (hereinafter referred to as “EDID”), and a DDC (Display Data Channel) control system signal used to exchange an encryption key called an HDCP (High-bandwidth Digital Content Protection). Since this DDC control system signal is a DC signal or a low-speed signal of lower than 100 KHz, and is a bidirectional signal. The DDC control system signal may be transmitted through a metal cable such as a LAN (Local Area Network) cable.
Namely, when transmitting the serial data signal of digital video, different kinds of cables may be used to transmit the video signal and the DDC control system signal, respectively.
The HDCP is a type of digital copyright management technology that functions to prevent illegal copying by encrypting a digital type image or an output signal of video content.
Also, the DDC is a standard for exchanging various kinds of information between the display and the PC for realizing PnP (Plug and Play). According to the DDC, information representing permissible resolution of a display, color depth, a scanning frequency, and a model number of a product is exchanged between the PC (video source device) and the display (sink device). Through the exchange of the information, setting information of the display is transferred, and thus the setting is automatically performed to match the performance of the respective displays.